This very preliminary study aimed at measuring the electric field generated by rhythmically contracting tissue. The goal was to assess the strength of this field and relate these values to marine predators using electroreception to locate prey. These initial experiments met with only limited success. This was primarily due to lack of time at the end of a busy summer but there were also problems in restraining the subject. Here we tried to scan the carapace over the heart of the green crab. Regretably the animal had a tendency to destroy the electrode assembly. Dr. Halstead will be returning to the MBL next summer when a more robust and effective restraining device will be designed.